1. Field of the Invention
The present invention relates to a CPP (current perpendicular to the plane) type magnetic detecting element that allows a sense current to flow in a direction perpendicular to the surface of a film, and more specifically, to a magnetic detecting element that can make greater the product ΔRA of the resistance variation and area of the element.
2. Description of the Related Art
FIG. 5 is a partially cross-sectional view of a conventional magnetic detecting element (spin valve type thin film element) when it is cut from the direction parallel to a surface facing a recording medium.
Reference numeral 1 shown in FIG. 5 is a foundation layer made of Ta, and a seed layer 2 made of a metal having a bcc structure (body-centered cubic structure), such as Cr, is formed on the foundation layer 1.
On the seed layer 2, a multilayer film T in which an antiferromagnetic layer 3, a fixed magnetic layer 4, a nonmagnetic material layer 5, a free magnetic layer 6, and a protective layer 7 are laminated sequentially is formed.
The protective layer 7 is formed of Ta, the nonmagnetic material layer 5 is formed of Cu, the free magnetic layer 6 and the fixed magnetic layer 4 are formed of an NiFe alloy, and the antiferromagnetic layer 3 is formed of PtMn.
Electrode layers 10 and 10 are provided on the top and bottom sides of the multilayer film T, and a sense current as a direct current is allowed to flow in a direction perpendicular to the surface of the multilayer film.
An exchange-coupling magnetic field is generated at the interface between the antiferromagnetic layer 6 and the fixed magnetic layer 5, and magnetization of the fixed magnetic layer 5 is fixed in a height direction (Y-direction).
Hard bias layers 8 made of a hard magnetic material, such as CoPt, are formed on opposite sides of the free magnetic layer 6, and the top, bottom, and end of each hard bias layer 8 are insulated by an insulating layer 9. Magnetized directions of the free magnetic layer 3 are arranged in a track width direction (X-direction in the drawing) by a longitudinal bias electric field from the hard bias layers 8.
If an external magnetic field is applied to the magnetic detecting element shown in FIG. 5, the magnetized direction of the free magnetic layer changes relatively with respect to the magnetized direction of the fixed magnetic layer, and the resistance value of the multilayer film changes. When a sensing current with a fixed current value is flowing, the external magnetic field is detected by detecting the change of the resistance value as a voltage change.
In many cases, a permalloy having an excellent soft magnetic property was used as a material of the free magnetic layer of the magnetic detecting element. Further, an example of the magnetic detecting element having a free magnetic layer made of an NiFe alloy other than the permalloy is described (see JP-A-2002-204010 (US Pub. No. 2002/0055016)).
The permalloy is an NiFe alloy containing Ni of about 80 at %. Further, in JP-A-2002-204010 (US Pub. No. 2002/0055016), in Paragraph 0023, the free magnetic layer is formed of an NixFe(100-X) alloy (40≦X≦70).
However, even if the free magnetic layer is formed using the NiFe alloy in this range of composition, it was difficult to control the product ΔRA of the resistance variation of a CPP (Current Perpendicular to the Plane)—GMR magnetic detecting element in which a sensing current as a direct current is allowed to flow perpendicularly to the surface of the multilayer film, and the area of the element so as to be 5 mΩμm2 or more. As a result, a practical producing output cannot be obtained.